This invention relates to telecommunication networks in general and to the transport network of a mobile telephone network. ATM cells are used for transmission of data. The payload of an ATM cell comprises mini cells.
To day the size of mini cells to be used for an individual connection is explicit indicated in each one of the mini cells of said individual connection. Typically 6 to 10 bits are used for size indication. The size information is of static nature, i.e. it does not change, as long as the mini cells don""t change size.
It is sometimes necessary to modify the size of a mini cell during an established connection. For example, the speech rate should be changed from full to half, or should the service be changed from speech to data or should a variable rate speech codec be used or should congestion of the traffic between two nodes be reduced by making the mini cells of all connections between said nodes smaller.
The explicit method of indicating mini cell size means that the bits used for size indication are overhead costs as regards the efficiency with which available band width is used as well as regards the efficiency with which mini cell size is indicated.
A main object of the invention is to provide a method for inicating the size of mini cells pertaining to an individual connection only when needed. In accordance with the invention indication of the mini cell size is needed only at instants when-the mini cell size is changed. At such instants the new mini cell size to be used for the following mini cells of the connection are indicated.
Another object of the invention is to provide a method of dynamically changing the size of a mini cell during an ongoing connection.
Another object of the invention is to provide a method for changing the size of a mini cell belonging to an individual connection with the aid of a mini cell. A mini cell used for this purpose is called a control mini cell.
Another object of the invention is to provide a method by which the control mini cell is sent in a control channel different from the channel in which mini cells containing user data are transported.
Still another object of the invention is to provide a method by which the control mini cell is transported in the same channel as that in which mini cells containing user data are transported.
A further object of the invention is to provide a synchronization mechanism for effecting change of mini cell size of an individual, ongoing connection. In particular the synchronization mechanism is intended to be used when the control mini cells are transported in a channel which is different from the channel in which mini cells containing user data mini cells are
In a mobile telephone system that uses ATM cells in the transport network reduced bandwidth or enhanced use of the available bandwidth will make it possible to add more channels into the system.
A large number of connections, which require a larger CID field, will increase the bandwidth gain if statistical multiplexing is used.